Method of setting and operating safety-valves.



o. s. J ACOBUS. METHOD OF SETTING AND OPERATING SAFETY VALVES.

APPLICATION FILED APR- 7. I917.

1,281,017. I Patented Oct. 8, 1918" W A TTORNEYS.

DAVID S. JACOIB'US, OF JERSEY CITY, NEW JERSEY, .ASSIGNOR TO THE BABGOCK& WILCOX COMPANY, OF BAYONNE, NEW JERSEY, A'CORPORATION OF NEW JERSEY.

METHOD OF SETTING AND OPERATING SAFETY-VALVES.

Specification of Letters Patent.

Patented Oct. 8, 1918.

Application filed April 7, 1917. Serial No. 160,370.

To all whom it may concern.

Be it known that I, DAVID S. JACOBUS, a citizen of the United States,residing at J ersey City, in the county of Hudson and State of NewJersey, have invented certaln new and useful Improvements in Methods ofSetting and Operating Safety-Valves, of which the following is aspecification,

It is well known that a safety valve must have relieving capacity atleast equal to the boiler evaporation at the pressure at which the valveis set to blow off, as otherwise the boiler pressure will continue torise with consequent danger of explosion, and modern boiler practice, bywhich boilers are being run at higher and higher capacities,necessitates the use of an increasing number of safety valves upon agiven boiler. Thus, in a 1000 H. P. boiler, eight or ten safety valvesof four and a half inches in diameter may be required. In the presentforms of spring pop safety valves the valve will not shut at the samepressure at which it opens,

and the pressure must fall below the pressure at which the valve opensbefore it will close. For example, if a valve is set to open at 200pounds steam pressure per square inch, it may not close until thepressure falls to 194 pounds per square inch. The difference in pressurebetween that at which the valve opens and at which it' closes is calledthe blow-down pressure. In applying safety valves to a boiler the mostimportant requirement is that the pressure shall not rise over a certainfixed amount, and in addition to this in order to avoid undue lossesthrough the blowing away of steam, the valve or valves must be so aranged as to prevent an undue amount of blow down pressure. The purposeof the present invention is to provide a method of setting and operatingsafety valves to materially reduce the number required, for a givenboiler, below that called for by present day practice.

Most large sized spring pop safety valves give a freeo ening for thepassage of steam of an area about one-tenth to one-sixth the area of thesteam connection to which they are attached. Should a greater opening beprovided the blow down pressure becomes too great. It is a comparativelyeasy matter to construct a valve having a high capacity with more thanthe usual amount of blow down pressure, but the difiicult part of theproblem has been to construct such a valve with a high capacity, whichmeans a high 11ft, wlthout exceeding the usual specified blow downpressure of about six to' eight that it becomes worn or is thrown out ofadjustment. It is necessary therefore with spring pop safety valves, asnow constructed, to restrict the amount of blow down pressure to preventundue waste in efficiency when the valve blows. But restricting theamount of blow down pressure limits the capacity of the valve to theextent above indicated when the valve is given a free area or lift ofonly about one-tenth to one-sixth the area of the steam connection. Bythe present invention it is, however, possible to provide a greater blowdown pressure of say ten to fifteen pounds, and the valves may be madeto open so as to have a considerably greater lift than is possible withthe usual valves having a blow down pressure of six to eight pounds, sothat a less number of safet valves may be safely. and economically useupon a given boiler, than is possible with valves as now constructed andset.

The invention will be understood from the following description taken inconnection with the accompanying drawings in.

which Figure 1 illustrates an arrangement of three safety valves upon asingle steam drum, and Fig. 2 an arrangement wherein the valves aremounted upon Y fittings.

In Fig. 1 the letters A, B and C designate safety valves set on a singlesteam drum D of a boiler. To illustrate the principle of my invention itmay be assumed that the valve A is set to blow at 200 pounds steampressure, the valve B at 204 pounds steam pressure, and the valve C at208 pounds steam ressure. It may also be assumed that the vali e A has ablow down pressure of six pounds, that is on blowing at 200 poundspressure per square inch it will close at 194 pounds per square inch.The valve B may.

blow down pressure of fourteen of ten'pouznds, and the valve C a blowdown pressure of fourteen pounds, so that if the three valves are allmade to blow they will all close at or about the same pressure, namely,194. pounds per square 1nch. In thls way the valves B and C may readllyhave progressively greater rellevlng capacities than the valve A byreason of the fact that a greater blowdown pressure is "allowed them; Ifthe valve A has a lift of 0.13 inch, the valve-B may'have a lift of say0.20 nch termines the minimum pressure to which the boiler must be blowndown, a greater relieving capacity can be obtamed with a glven number ofvalves constructed and arranged as described with correspondingly;improved results, so that with a glven boiler a less number of safetyvalves will be required, with however the same results as with a largernumber of the usual construction and setting as now employed.

A modified form of setting is shown in Fig. 2 in which the valves E, F,Gr and H are-mounted on Y fittings I and J above the "steam drum K.These valves may be set in series arranged for difl'erent amounts ofblow down and varying capacities. lln cominon with the arrangement'shownin Fig. 1,

a greaterrelieving capacity may be obtained for a given number of valvesfor a glven amount of blow down pressure. If desired,

corresponding valves on each Y fitting may be set for the same amount ofblow down pressure, that is, one of the valves on a given Y fitting mayhave a blow down pressure of say six pounds, and the other a blow downpressure of say ten pounds. This will enable the construction of the twovalves for each Y fitting so that their combined capacity will begreater than the combined capacity of two valves each having a blow downpressure of six pounds. The idea suggested might be carried stillfurtherby installing the valves in groups of three or more.

The above specification describes valves of the same areafor which thevariation in relieving capacity is secured through providing differentamounts of lift. If desired, Valves of varying diameters may beemployed.

Several valves may also be inserted in the same casing and used in placeof two valves on a Y fitting. I

If desired, the valve which is set at the highest pressure on a boilerand which is the last to blow, could be made a special or emergencyvalve that would give a relatively high lift with a blow-down ressurethat would be so great that this va ve would not close as soon as theothers. A hand lever attachment could be placed on this special valvewhichcould be used for closing the valve by hand after the pressure isreduced ,to that at which the other valves close. A

valve of the sort to be closed by hand could be made to give the, fullarea of the opening of the steam pipe which leads to it and should theother valves on the boiler fail to discharge enough steam to prevent thepressure rising to a point where the special valve will open, theopening of the special valve would surely prevent any further increaseof pressure through its relatively large relieving capacity.

' Where valves are set in series in the way proposed, the valves whichare at the highest pressure are only called on to act in an extremeemergency, and in modern practice such valves may practically neveropen, or open say only once in one or two years, this arising throughthe fact that there must be some unusual occurrence which requires thesteam to be shut off from the entire plant,

and this with the boilers running at their maximum capacity in orderthat the safety valves may be called on to release the maximum capacity.As such occurrences are rare it can readily be seen that the valveswhich are set the highest in the series are seldom called on to act, orpossibly may never be called on to act. It would therefore be nohardship as far as operating the steam plant is concerned to close thevalves which are set at the highest pressure by hand should anoccurrence arise that caused such special or emergency valves to open.

Safety valves are provided with hand levers for opening the valves byhand in order to make sure that-the valve does not.

become stuck to its seat. This is done daily 1n many plants in order tomake sure that the safety valves are. in proper adjustment. The samelevers that are used for opening the valves as described could beemployed for closing the special or emergency valve.

What ll claim and desire to secure by Letters Patent of the UnitedStates is: 1. The herein described method consistmg 1n arranging safetyvalves upon a boiler so that they shall have progressively increasinglifts with increasing blow-down pressures and correspondingly increasedrelievmg capacities.

2. The herein described method consisting in arranging safety valvesupon a boiler with progressively increasing lifts and correspondinglyincreased relieving capacities, and with progressively increasing blowdown pressures.

3. The method of controlling the pressure of a steam boiler whichconsists in providing the same with a plurality of safety valves, andregulating said valves to open at different steam pressures and to closeat substantially the same steam pressure.

4. The method of controlling the pressure of a steam boiler whichconsists in providing the same with a series of safety valves, andregulating said valves so that they shall have progressively increasingblow off capacities, and correspondingly increasing blow down pressures.v

5. A steam boiler having at least two safety valves, one of said valveshaving a greater lift and a'greater blow down pressure than the other,with correspondingly increased relieving capacity.

6. A boiler having at least two safety valves, one of said valves beingset to open at a difi'erent'steam pressure from'the other valves, andboth valves being arranged to blow down to substantially the same steampressure.

7. A boiler having a lurality of safety valves with progressive yincreasing lifts and greater blow-down pressures and correspondinglyincreased relieving capacities.

.8. A boiler having a plurality of. safety valves .with progressivelyincreasing lifts and correspondingly increased relieving capacities,said valves being arranged with progressively increasing blow-downpressures.

9. A boiler having a plurality of safety valves arranged to open atprogressively increasing steam pressures and correspond ingly increasingblow-down pressures.

10. A boiler having a plurality of safety valves including one ofrelatively high steam relieving capacity tobe used as an emergencyvalve, s'aid special valve being arranged to blow in case the othervalves cannot fully discharge the steam generated, and means for closingsaid special valve by hand after blowing.

11. A boiler having a plurality of safety valves with progressivelyincreasing lifts and correspondingly increased relieving capacities, thelast valve to blow having means by which it may be closed by hand afterit has opened and the steam pressure has fallen the desired amount.

In testimony whereof I have hereunto signed my name in the presence oftwo sub scribing witnesses.

DAVID S. JACOBUS. Witnesses:

EDITH CAMP, JOHN A. W. DIXON.

